The present invention refers to a device for controlling winding of a log in a re-reeling machine.
In machines or assemblies for winding paper for household use, such as toilet paper, absorbent wipes, towelettes, serviettes, handkerchiefs and the like, elements are provided which guide the paper being fed and control proper winding thereof on a central core, or in any case winding thereof to form a finished roll of pre-set size even without a core, the said roll usually being referred to as xe2x80x9clogxe2x80x9d.
It is known that in these machines, the so-called re-reeling machines, designed to form the aforesaid rolls of paper or logs, are generally provided with two winding rollers designed to co-operate with a third roller. The first two rollers simply determine winding of the paper into a roll progressively increasing in diameter, whilst the third roller, in addition to co-operating with the winding operation, has the function of exerting a certain pressure on the roll or log, ensuring the required compacted winding of the latter.
The first two rollers have a fixed position with respect to the outer frame and contribute to supporting the log and to drawing the paper through. The third roller, acting as a pressure roller, exerts a pressure on the log being formed, and hence determines the diameter of the finished product.
In order to do this, the third roller, generally referred to as xe2x80x9cpressure rollerxe2x80x9d is supported on opposite ends of at least one pair of arms pivoted to the frame. The third roller is thus free to oscillate according to a curved direction about the pivoting of the arms, and the pressure acting on the roller can be controlled by means of a sensor.
For the winding to be of good quality, the finished roll of paper must be contained between the three rollers, and the output gap from the above-mentioned arrangement of three rollers for winding the roll must be slightly smaller than the diameter of the finished log.
This arrangement is necessary for ensuring that, during output, the log or roll of paper will undergo a slight squeezing such as to guarantee contact with the third roller or pressure roller throughout the exchange stage (i.e., end of log, ejection of finished log, and start of winding of subsequent log).
This fairly precise sizing of the output gap is rather important in so far as if the gap were too narrow, the squeeze would be excessive, with consequent ovalization of the finished product. In the case of a gap that is too large, even though the squeeze would be reduced, there might occur a loss of contact between the winding pressure roller and the log, with possible exit of the latter from the set of three rollers before winding is completed.
In addition, the fact should be considered that, with the arrangement of three rollers currently in use, control and containment of the log is increasingly more difficult as the diameter of the finished product increases. In fact, the known arrangement in general enables a good quality of winding up to diameters of the finished product of around 110 mm, and not more.
A purpose of the present invention is therefore to provide a device for controlling winding of a log in a re-reeling machine which will overcome the drawbacks referred to above, working in a highly satisfactory way even as the diameter of the roll varies.
Another purpose of the present invention is to have available a device which, albeit enabling optimal output of the roll with minimal squeeze, works efficiently also for roll diameters exceeding 110 mm.
Yet another purpose of the present invention is to provide a device which, albeit overcoming the drawbacks referred to previously, makes it possible even so to obtain minimal squeezing of the finished roll, within the tolerances according to the requirements.
These purposes according to the present invention are achieved by providing a device for controlling winding of a log in a paper re-reeling machine, as specified in claim 1.
Further, more detailed, characteristics are specified in the subsequent claims.